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Introduction to Cancer

The major features of this chapter are the clinical aspects of cancer, including etiology, prevention, staging, diagnosis, and treatment of common cancers; and recognition and management of complications from cancer.

ETIOLOGY

Cancer is the second most common cause of death in the United States. In 2020, an estimated 1,806,590 cases of cancer were diagnosed, and 606,520 persons died of cancer. Based on current statistics, almost 40% of Americans will be diagnosed with cancer at some point during their lifetime. Table 39–1 lists the 10 leading cancer types in men and women by site.

Table 39–1.Estimated 10 most common cancer cases in the United States in males and females (all races).

However, death rates from cancers are declining. Compared to the 1991 overall cancer death rate of 215.1 per 100,000 population, the 2017 rate of 152.4 per 100,000 represents a 29% reduction in the overall cancer death rate. Importantly, death rates have declined in all four of the most common cancer types (lung, colorectum, breast, and prostate). Reductions in cancer mortality reflect successful implementation of a broad strategy of prevention, detection, and treatment. Due to these improvements, the number of cancer survivors is increasing. In 2015, an estimated 14.5 million people were alive in whom cancer had been previously diagnosed; that number is projected to grow to 18.9 million in 2024.

MODIFIABLE RISK FACTORS

Tobacco is the most common preventable cause of cancer death; at least 30% of all cancer deaths in the United States are directly linked to tobacco. In 2014, an estimated 167,133 cancer deaths in the United States could be directly attributed to tobacco. Clear evidence links tobacco use to at least 15 cancers. The most dramatic link is with lung cancer; 80% of lung cancer deaths are attributable to smoking. Remarkably, almost 10% of long-term survivors of a tobacco-related cancer continue to use tobacco products, increasing their risk of yet another cancer.

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